Electrochemical-assisted green leaching method of retired lithium ion battery

Abstract

A method for electrochemically assisted green leaching of a decommissioned lithium ion battery belongs to the technical field of decommissioned lithium battery key metal recycling and decommissioned battery recovery, and specifically comprises the following steps: disassembling a decommissioned ternary lithium battery, taking out a positive electrode material, cleaning, drying and grinding the positive electrode material to obtain a positive electrode material; placing the mixture and a weak acid solution in a reaction container to form a leaching system; mounting an inert electrode in the reaction container, connecting an external direct-current power supply, and gradually adjusting the voltage according to the potential requirement of metal ion dissolution to respectively leach nickel ions, cobalt ions and manganese ions to obtain a multi-metal-containing pregnant solution; and adding a precipitant into the obtained solution for precipitation to generate lithium carbonate precipitate, filtering, washing, drying and recovering to obtain the high-purity lithium compound. According to the method, use of strong acid and complex chemical reagents is reduced, the complexity of waste liquid treatment is remarkably reduced, and efficient recovery of target metal is achieved by controlling the metal dissolution process step by step.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling key metals from retired lithium batteries and retired battery recycling technology, and specifically relates to a method for electrochemically assisted green leaching of retired lithium-ion batteries. Background Art

[0002] With the rapid development of the market scales of electric vehicles, electronic products, etc., the number of retired ternary lithium batteries has increased sharply, and efficient recycling has become an important issue in the industry. Retired lithium-ion batteries contain various key metals such as nickel, cobalt, lithium, and manganese. In particular, nickel and cobalt are precious and scarce metal resources and have high recycling value.

[0003] Most of the existing recycling methods for retired ternary lithium batteries adopt acidic chemical leaching technology. By applying an electric field in an acidic leaching system and using potential control, the step-by-step and selective dissolution of metals such as nickel, cobalt, and manganese can be achieved. At a specific voltage, electrochemical leaching can effectively control the preferential precipitation of specific metal ions, reduce the co-dissolution of impurities, and significantly simplify the subsequent separation and purification processes. The electrochemically assisted leaching technology meets the requirements of the modern retired battery recycling towards the green and sustainable direction and has gradually become a research hotspot in the field of retired lithium battery recycling.

[0004] Patent CN119040659A proposes a lithium leaching process based on the synergistic effect of acid solution and oxidant, and realizes the efficient recycling of lithium through multiple leaching steps. However, its process relies on a strong acid system (such as sulfuric acid) and requires multi-stage chemical impurity removal, which may introduce risks of equipment corrosion and complexity of waste liquid treatment. The present invention innovatively uses a weak acidic citric acid solution to replace the traditional strong acid system, combined with electrochemically stepwise potential regulation, to achieve the selective step-by-step dissolution of nickel, cobalt, and manganese at room temperature. Through the synergistic effect of precise potential control and weak acid environment, the present invention abandons the dependence on complex reagents, significantly reduces the equipment corrosivity and waste liquid toxicity, and simplifies the subsequent separation process. In addition, lithium resources are efficiently recycled by the sodium carbonate precipitation method, taking into account environmental protection and economy on the basis of reducing energy consumption by more than 30%, and providing a more competitive solution for the green industrial recycling of retired lithium batteries. Summary of the Invention

[0005] Aiming at the problems existing in the current recycling technologies of retired power batteries, the present invention relates to a method for electrochemically assisted green leaching of retired lithium-ion batteries, aiming to solve the problems of environmental pollution, high energy consumption and poor selectivity in the metal recycling process of current ternary lithium batteries. Based on the electrochemically assisted technology, in a weakly acidic environment, by applying an appropriate potential, the selective dissolution of metals such as nickel, cobalt, and manganese in the cathode material of retired ternary lithium batteries is achieved. The present invention not only reduces the use of strong acids and complex chemical reagents, significantly reduces the complexity of waste liquid treatment, but also realizes the efficient recovery of target metals by stepwise controlling the metal dissolution process.

[0006] To achieve the above object, the present invention provides a method for electrochemically assisted green leaching of retired lithium-ion batteries, which specifically includes the following steps:

[0007] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the cathode material, clean, dry it, grind it to D50 = 2μm - 5μm, and place it in a reaction vessel;

[0008] (2) Configure the leaching solution: Place the weak acid solution as the leaching solution in the reaction vessel to form a leaching system;

[0009] (3) Electrode installation and electric field setting: Install an inert electrode in the reaction vessel, connect an external DC power supply, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions;

[0010] (4) Dissolution of nickel ions: Adjust the power supply potential to dissolve nickel ions from the leaching system to generate a leaching solution containing nickel ions; During the dissolution process, regularly sample and analyze the ion concentration in the leaching solution. When the change in ion concentration tends to be stable, the dissolution ends;

[0011] (5) Dissolution of cobalt ions: After the dissolution of nickel is completed, adjust the potential to dissolve cobalt ions from the leaching system to generate a leaching solution containing cobalt ions;

[0012] (6) Dissolution of manganese ions: After the dissolution of cobalt is completed, adjust the potential to dissolve manganese ions from the leaching system to generate a leaching solution containing manganese ions, and maintain this potential to ensure the complete dissolution of manganese ions to obtain a multi-metal rich solution;

[0013] (7) Precipitation for lithium extraction: Add a precipitant to the solution obtained in step (6) for precipitation to generate lithium carbonate precipitate, and recover it through filtration, washing and drying to obtain a high-purity lithium compound.

[0014] Wherein:

[0015] In the step (2), the weak acid solution is citric acid or malic acid solution, and the concentration is 0.2mol / L - 0.5mol / L.

[0016] In the said step (3), the material of the inert electrode is selected from platinum, titanium and graphite.

[0017] In the said step (3), the initial voltage of the DC power supply is 0.5V - 3V.

[0018] In the said step (4), during the nickel ion dissolution process, the power supply potential is 0.6V - 1.0V, and the leaching rate of nickel is 90% - 98%.

[0019] In the said step (5), during the cobalt ion dissolution process, the power supply potential is 1.2V - 1.6V, and the leaching rate of cobalt is 85% - 95%.

[0020] In the said step (6), during the manganese ion dissolution process, the power supply potential is 1.8V - 2.2V, and the leaching rate of manganese is 80% - 95%.

[0021] During the dissolution processes of the said nickel ions, cobalt ions and manganese ions, samples are regularly taken to analyze the ion concentration in the leaching solution. When the change in ion concentration tends to be stable, the dissolution ends.

[0022] In the said step (7), the precipitant is a sodium carbonate solution with a concentration of 0.05mol / L - 0.2mol / L, and the recovery rate of lithium obtained is 95% - 98%.

[0023] Compared with the existing comprehensive recycling processes for retired power batteries, the features and advantages of the present invention are as follows:

[0024] 1. By applying an electric current in a weak acid solution, the present invention enables metal ions to be rapidly dissolved and transferred into the solution under the action of electrochemistry. Compared with traditional high-temperature roasting or wet acid leaching methods, the present invention can significantly reduce energy consumption because the electrochemical reaction can be carried out at normal or low temperatures, avoiding the energy consumption and equipment requirements of the high-temperature heating process. In particular, the electrochemical-assisted leaching can be efficiently carried out under lower current and voltage conditions, reducing the energy waste caused by high-temperature roasting and long-time reactions in traditional methods.

[0025] 2. The solution provided by the present invention reduces the generation of acidic waste liquid during the leaching process, and the waste liquid composition is relatively single and easy to treat. Through appropriate treatment, the resource utilization of the waste liquid can be realized, reducing the risk of secondary pollution and the cost of waste liquid treatment, and having good environmental and economic benefits.

[0026] 3. The present invention can efficiently and selectively dissolve metals such as lithium, nickel, cobalt, and manganese in a weakly acidic environment. The electrochemical effect can promote the reduction reaction and redox reaction of metals, improve the dissolution rate and selectivity of metal ions, and reduce the problem of co-dissolution of metal ions. This makes the separation of different metals more efficient. Especially in a multi-metal mixed solution, by adjusting the current density and voltage, the step-by-step recovery of metals can be achieved, ensuring an increase in the metal recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Process flow chart of an electrochemical-assisted green leaching method for retired lithium-ion batteries of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The technical solutions in the patent implementation will be clearly and completely described below in conjunction with the embodiments and the drawings. It should be noted that the embodiments described in the present invention are only used for further explanation and illustration, rather than limiting its application scope. Based on the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0029] Embodiment 1

[0030] In this embodiment, the retired ternary lithium battery comes from a certain technology company in Guangdong. Its Li content is 3.59%, Co content is 4.59%, Mn content is 9.58%, Ni content is 17.15%, and C content is 40.20%. C mainly exists in the form of graphite.

[0031] An electrochemical-assisted green leaching method for retired lithium-ion batteries, the process flow chart of which is as Figure 1 shown, and specifically includes the following steps:

[0032] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2 μm - 5 μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained positive electrode material particles are placed in a reaction vessel for standby.

[0033] (2) Prepare the leaching solution: Use a citric acid solution with a concentration of 0.3 mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0034] (3) Electrode installation and electric field setting: Install a platinum electrode in the reaction vessel to ensure its stability in a weakly acidic environment, connect an external DC power supply, set the initial voltage to 2V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0035] (4) Nickel ion dissolution: Adjust the power supply potential to 0.8V to dissolve nickel ions from the leaching system, generating a leaching solution containing nickel ions; during the dissolution process, sample and analyze the nickel ion concentration in the leaching solution regularly. When the change in nickel ion concentration tends to be stable, the dissolution is completed.

[0036] (5) Cobalt ion dissolution: After the nickel dissolution is completed, adjust the potential to 1.4V to dissolve cobalt ions from the leaching system, generating a leaching solution containing cobalt ions; during the dissolution process, sample and analyze the cobalt ion concentration in the leaching solution regularly. When the change in cobalt ion concentration tends to be stable, the dissolution is completed.

[0037] (6) Manganese ion dissolution: After the cobalt dissolution is completed, adjust the potential to 2.0V to dissolve manganese ions from the leaching system, generating a leaching solution containing manganese ions. Maintain this potential to ensure complete dissolution of manganese ions, obtaining a precious liquid containing multiple metals; during the dissolution process, sample and analyze the manganese ion concentration in the leaching solution regularly. When the change in manganese ion concentration tends to be stable, the dissolution is completed.

[0038] (7) Lithium precipitation: Add a sodium carbonate solution with a concentration of 0.1mol / L to the solution obtained in step (6) for precipitation, generating lithium carbonate precipitation, which is recovered through filtration, washing, and drying to obtain a high-purity lithium compound.

[0039] In this example, the leaching rates of Ni, Co, and Mn in the leaching solutions of various transition metals are 95.78%, 90.36%, and 87.25% respectively. The recovery rate of lithium obtained by the sodium carbonate precipitation method is 97.16%, meeting the requirements of battery-grade lithium materials.

[0040] Example 2

[0041] In this example, the retired ternary lithium battery comes from a certain technology company in Hunan. Its Li content is 3.87%, Co content is 3.16%, Mn content is 5.22%, Ni content is 22.47%, and C content is 35.36%. C is mainly present in the form of graphite.

[0042] A method for electrochemically assisted green leaching of retired lithium-ion batteries specifically includes the following steps:

[0043] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2μm - 5μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of metals. The obtained positive electrode material particles are placed in a reaction container for standby.

[0044] (2) Prepare the leaching solution: Use a citric acid solution with a concentration of 0.4mol / L as the leaching solution and place it in a reaction container to provide a moderate acidic environment and form a leaching system.

[0045] (3) Electrode installation and electric field setting: Install graphite electrodes in the reaction vessel to ensure their stability in a weakly acidic environment. Connect an external DC power supply, set the initial voltage to 2V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0046] (4) Nickel ion dissolution: Adjust the power supply potential to 0.8V to dissolve nickel ions from the leaching system, generating a leaching solution containing nickel ions. During the dissolution process, regularly sample and analyze the nickel ion concentration in the leaching solution. When the change in nickel ion concentration tends to be stable, the dissolution is completed.

[0047] (5) Cobalt ion dissolution: After the nickel dissolution is completed, adjust the potential to 1.4V to dissolve cobalt ions from the leaching system, generating a leaching solution containing cobalt ions. During the dissolution process, regularly sample and analyze the cobalt ion concentration in the leaching solution. When the change in cobalt ion concentration tends to be stable, the dissolution is completed.

[0048] (6) Manganese ion dissolution: After the cobalt dissolution is completed, adjust the potential to 2.0V to dissolve manganese ions from the leaching system, generating a leaching solution containing manganese ions. Maintain this potential to ensure complete dissolution of manganese ions, obtaining a multi-metal rich solution. During the dissolution process, regularly sample and analyze the manganese ion concentration in the leaching solution. When the change in manganese ion concentration tends to be stable, the dissolution is completed.

[0049] (7) Lithium precipitation: Add a sodium carbonate solution with a concentration of 0.1mol / L to the solution obtained in step (6) for precipitation to form lithium carbonate precipitate, which is recovered through filtration, washing, and drying to obtain a high-purity lithium compound.

[0050] In this example, the leaching rates of Ni, Co, and Mn in the leaching solutions of various transition metals are 96.97%, 89.43%, and 85.54% respectively. The recovery rate of lithium obtained by the sodium carbonate precipitation method is 97.49%, meeting the requirements of battery-grade lithium materials.

[0051] Example 3

[0052] In this example, the retired ternary lithium battery comes from a certain technology company, with a Li content of 4.56%, a Co content of 3.25%, a Mn content of 4.59%, a Ni content of 22.23%, and a C content of 38.09%. The C mainly exists in the form of graphite.

[0053] A method for electrochemically assisted green leaching of retired lithium-ion batteries specifically includes the following steps:

[0054] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the cathode material, wash, dry it, and then grind it to D50 = 2μm - 5μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained cathode material particles are placed in a reaction vessel for standby.

[0055] (2) Preparation of leaching solution: Use a malic acid solution with a concentration of 0.5mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0056] (3) Electrode installation and electric field setting: Install titanium electrodes in the reaction vessel to ensure the stability of the electrodes in a weakly acidic environment, connect an external DC power supply, set the initial voltage to 2.5V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0057] (4) Dissolution of nickel ions: Adjust the power supply potential to 0.8V to dissolve nickel ions from the leaching system to generate a leaching solution containing nickel ions; during the dissolution process, regularly sample and analyze the nickel ion concentration in the leaching solution. When the change in nickel ion concentration tends to be stable, the dissolution ends.

[0058] (5) Dissolution of cobalt ions: After the dissolution of nickel is completed, adjust the potential to 1.5V to dissolve cobalt ions from the leaching system to generate a leaching solution containing cobalt ions; during the dissolution process, regularly sample and analyze the cobalt ion concentration in the leaching solution. When the change in cobalt ion concentration tends to be stable, the dissolution ends.

[0059] (6) Dissolution of manganese ions: After the dissolution of cobalt is completed, adjust the potential to 2.1V to dissolve manganese ions from the leaching system to generate a leaching solution containing manganese ions, and maintain this potential to ensure the complete dissolution of manganese ions to obtain a multi-metal rich solution; during the dissolution process, regularly sample and analyze the manganese ion concentration in the leaching solution. When the change in manganese ion concentration tends to be stable, the dissolution ends.

[0060] (7) Precipitation for lithium extraction: Add a sodium carbonate solution with a concentration of 0.1mol / L to the solution obtained in step (6) for precipitation to form lithium carbonate precipitate, and recover it through filtration, washing, and drying to obtain a high-purity lithium compound.

[0061] In this example, the Ni leaching rate in each transition metal leaching solution is 94.49%, the Co leaching rate is 90.28%, and the Mn leaching rate is 90.64%. The recovery rate of lithium obtained by the sodium carbonate precipitation method is 96.99%, meeting the requirements of battery-grade lithium materials.

[0062] Example 4

[0063] In this embodiment, the retired ternary lithium battery comes from a certain technology company. Its Li content is 3.89%, Co content is 3.21%, Mn content is 5.17%, Ni content is 20.67%, and C content is 38.61%. C is mainly present in the form of graphite.

[0064] An electrochemical-assisted green leaching method for retired lithium-ion batteries specifically includes the following steps:

[0065] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2μm - 5μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained positive electrode material particles are placed in a reaction vessel for standby.

[0066] (2) Prepare the leaching solution: Use a citric acid solution with a concentration of 0.3mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0067] (3) Electrode installation and electric field setting: Install graphite electrodes in the reaction vessel to ensure the stability of the electrodes in a weakly acidic environment. Connect an external DC power supply, set the initial voltage to 2.3V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0068] (4) Dissolution of nickel ions: Adjust the power supply potential to 0.9V to dissolve nickel ions from the leaching system and generate a leaching solution containing nickel ions. During the dissolution process, regularly sample and analyze the nickel ion concentration in the leaching solution. When the change in nickel ion concentration tends to be stable, the dissolution ends.

[0069] (5) Dissolution of cobalt ions: After the dissolution of nickel is completed, adjust the potential to 1.6V to dissolve cobalt ions from the leaching system and generate a leaching solution containing cobalt ions. During the dissolution process, regularly sample and analyze the cobalt ion concentration in the leaching solution. When the change in cobalt ion concentration tends to be stable, the dissolution ends.

[0070] (6) Dissolution of manganese ions: After the dissolution of cobalt is completed, adjust the potential to 2.0V to dissolve manganese ions from the leaching system and generate a leaching solution containing manganese ions. Maintain this potential to ensure the complete dissolution of manganese ions and obtain a multi-metal rich solution. During the dissolution process, regularly sample and analyze the manganese ion concentration in the leaching solution. When the change in manganese ion concentration tends to be stable, the dissolution ends.

[0071] (7) Precipitation for lithium extraction: Add a sodium carbonate solution with a concentration of 0.1mol / L to the solution obtained in step (6) for precipitation to generate lithium carbonate precipitate, which is recovered through filtration, washing, and drying to obtain high-purity lithium compounds.

[0072] In this example, the leaching rate of Ni in each transitional metal leaching solution is 92.95%, the leaching rate of Co is 87.79%, and the leaching rate of Mn is 84.39%. The recovery rate of lithium obtained by the sodium carbonate precipitation method is 96.41%, meeting the requirements of battery-grade lithium materials.

[0073] Example 5

[0074] In this example, the retired ternary lithium battery comes from a certain technology company, with a Li content of 3.74%, a Co content of 3.78%, a Mn content of 5.67%, a Ni content of 20.14%, and a C content of 38.47%. C is mainly present in the form of graphite.

[0075] An electrochemical-assisted green leaching method for retired lithium-ion batteries specifically includes the following steps:

[0076] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2μm - 5μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained positive electrode material particles are placed in a reaction vessel for standby.

[0077] (2) Configure the leaching solution: Use a citric acid solution with a concentration of 0.3mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0078] (3) Electrode installation and electric field setting: Install a platinum electrode in the reaction vessel to ensure its stability in a weakly acidic environment, connect an external DC power supply, set the initial voltage to 2.3V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0079] (4) Dissolution of nickel ions: Adjust the power supply potential to 0.9V to dissolve nickel ions from the leaching system to generate a leaching solution containing nickel ions; during the dissolution process, regularly sample and analyze the nickel ion concentration in the leaching solution. When the change in nickel ion concentration tends to be stable, the dissolution ends.

[0080] (5) Dissolution of cobalt ions: After the dissolution of nickel is completed, adjust the potential to 1.6V to dissolve cobalt ions from the leaching system to generate a leaching solution containing cobalt ions; during the dissolution process, regularly sample and analyze the cobalt ion concentration in the leaching solution. When the change in cobalt ion concentration tends to be stable, the dissolution ends.

[0081] (6) Dissolution of manganese ions: After the dissolution of cobalt is completed, adjust the potential to 2.0V to dissolve manganese ions from the leaching system to generate a leaching solution containing manganese ions. Maintain this potential to ensure the complete dissolution of manganese ions and obtain a multi-metal rich solution; during the dissolution process, regularly sample and analyze the manganese ion concentration in the leaching solution. When the change in manganese ion concentration tends to be stable, the dissolution ends.

[0082] (7) Lithium precipitation: Add sodium carbonate solution with a concentration of 0.1 mol / L to the solution obtained in step (6) for precipitation to form lithium carbonate precipitate, which is recovered through filtration, washing and drying to obtain high-purity lithium compounds.

[0083] In this example, the leaching rate of Ni in the transition metal leaching solution is 96.47%, the leaching rate of Co is 87.79%, and the leaching rate of Mn is 84.39%. The recovery rate of lithium recovered by the sodium carbonate precipitation method is 97.48%, meeting the requirements of battery-grade lithium materials.

[0084] Example 6

[0085] In this example, the retired ternary lithium battery comes from a certain technology company, with a Li content of 3.94%, a Co content of 3.51%, a Mn content of 6.49%, a Ni content of 21.42%, and a C content of 40.21%. C is mainly present in the form of graphite.

[0086] An electrochemical-assisted green leaching method for retired lithium-ion batteries specifically includes the following steps:

[0087] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2 μm - 5 μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained positive electrode material particles are placed in a reaction vessel for standby.

[0088] (2) Preparation of leaching solution: Use citric acid solution with a concentration of 0.3 mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment to form a leaching system.

[0089] (3) Electrode installation and electric field setting: Install platinum electrodes in the reaction vessel to ensure the stability of the electrodes in a weakly acidic environment, connect an external DC power supply, set the initial voltage to 2.3 V, and gradually adjust the voltage according to the potential requirements for the dissolution of metal ions.

[0090] (4) Dissolution of nickel ions: Adjust the power supply potential to 0.9 V to dissolve nickel ions from the leaching system to form a leaching solution containing nickel ions; during the dissolution process, regularly sample and analyze the nickel ion concentration in the leaching solution. When the change in nickel ion concentration tends to be stable, the dissolution ends.

[0091] (5) Dissolution of cobalt ions: After the dissolution of nickel is completed, adjust the potential to 1.6 V to dissolve cobalt ions from the leaching system to form a leaching solution containing cobalt ions; during the dissolution process, regularly sample and analyze the cobalt ion concentration in the leaching solution. When the change in cobalt ion concentration tends to be stable, the dissolution ends.

[0092] (6) Manganese ion dissolution: After the cobalt dissolution is completed, adjust the potential to 2.0 V to dissolve manganese ions from the leaching system to generate a leaching solution containing manganese ions. Maintain this potential to ensure complete dissolution of manganese ions and obtain a multi-metal rich solution. During the dissolution process, regularly sample and analyze the manganese ion concentration in the leaching solution. When the change in manganese ion concentration tends to be stable, the dissolution is considered complete.

[0093] (7) Lithium precipitation: Add a sodium carbonate solution with a concentration of 0.15 mol / L to the solution obtained in step (6) for precipitation to form lithium carbonate precipitate, which is recovered through filtration, washing, and drying to obtain a high-purity lithium compound.

[0094] In this example, the leaching rate of Ni in the transition metal leaching solution is 96.76%, the leaching rate of Co is 86.99%, and the leaching rate of Mn is 85.09%. The recovery rate of lithium obtained by the sodium carbonate precipitation method is 96.65%, meeting the requirements of battery-grade lithium materials.

[0095] Comparative Example 1

[0096] In this example, the retired ternary lithium battery comes from a certain technology company in Guangdong. Its Li grade is 3.59%, Co content is 4.59%, Mn content is 9.58%, Ni content is 17.15%, and C content is 40.20%. C is mainly present in the form of graphite.

[0097] An electrochemical-assisted green leaching method for retired lithium-ion batteries specifically includes the following steps:

[0098] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean, dry, and grind it to D50 = 2 μm - 5 μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. Place the obtained positive electrode material particles in a reaction vessel for standby.

[0099] (2) Prepare the leaching solution: Use pure water at 25°C as the leaching solution and place it in a reaction vessel to form a leaching system.

[0100] (3) Electrode installation and electric field setting: Install a platinum electrode in the reaction vessel, connect an external DC power supply, apply a voltage of 1.0 V, and a current density of 10 mA / cm 2 , and the reaction time is 60 min.

[0101] (4) Lithium precipitation: Add a sodium carbonate solution with a concentration of 0.1 mol / L to the solution after the reaction in step (3) for precipitation to form lithium carbonate precipitate, which is recovered through filtration, washing, and drying to obtain a lithium compound.

[0102] In this comparative example, the leaching rates of nickel (Ni), cobalt (Co), and manganese (Mn) are all lower than 5%. The recovery rate of lithium recovered by the sodium carbonate precipitation method is 15.26%.

[0103] Compared with Example 1, since the solution is pure water and lacks an acidic medium, it is difficult to effectively dissolve metal ions, and the leaching rate is extremely low. This condition is not suitable for industrial recovery.

[0104] Comparative Example 2

[0105] In this example, the retired ternary lithium battery comes from a certain technology company in Guangdong. Its Li grade is 3.59%, Co content is 4.59%, Mn content is 9.58%, Ni content is 17.15%, and C content is 40.20%. C is mainly hosted in the form of graphite.

[0106] A leaching method for retired lithium-ion batteries specifically includes the following steps:

[0107] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, and then grind it to D50 = 2 μm - 5 μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained positive electrode material particles are placed in a reaction vessel for standby.

[0108] (2) Prepare the leaching solution: Use a dilute sulfuric acid solution with a concentration of 0.3 mol / L as the leaching solution. Control the temperature of the dilute sulfuric acid solution at 25°C and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0109] (3) Leaching of transition metal ions: Without applying voltage, leach only with the acidic solution in step (2), and the reaction time is 60 min.

[0110] (4) Precipitation for lithium extraction: Add a sodium carbonate solution with a concentration of 0.1 mol / L to the solution after the reaction in step (3) for precipitation to form lithium carbonate precipitate, and recover it through filtration, washing, and drying to obtain a lithium compound.

[0111] In this comparative example, the leaching rates of nickel (Ni), cobalt (Co), and manganese (Mn) are all lower than 80%. The recovery rate of lithium recovered by the sodium carbonate precipitation method is 50.26%.

[0112] Compared with Example 1, due to the lack of electrochemical assistance, the leaching rate has decreased, especially the leaching rates of nickel and cobalt are not ideal.

[0113] Comparative Example 3

[0114] In this example, the retired ternary lithium battery comes from a certain technology company. Its Li grade is 4.56%, Co content is 3.25%, Mn content is 4.59%, Ni content is 22.23%, and C content is 38.09%. C mainly exists in the form of graphite.

[0115] An electrochemical-assisted green leaching method for retired lithium-ion batteries specifically includes the following steps:

[0116] (1) Pretreatment: Disassemble the retired ternary lithium battery, take out the cathode material, clean, dry it, and then grind it to D50 = 2μm - 5μm to increase the contact area between the metal and the leaching solution and promote the subsequent dissolution of the metal. The obtained cathode material particles are placed in a reaction vessel for standby.

[0117] (2) Prepare the leaching solution: Use a malic acid solution with a concentration of 0.5mol / L as the leaching solution and place it in a reaction vessel to provide a moderate acidic environment and form a leaching system.

[0118] (3) Electrode installation and electric field setting: Install titanium electrodes in the reaction vessel to ensure the stability of the electrodes in an acidic environment. Connect an external DC power supply, set the high voltage to 1.5V, and the current density to 20mA / cm 2 , and the reaction time is 60min.

[0119] (4) Precipitate lithium: Add a sodium carbonate solution with a concentration of 0.1mol / L to the solution after the reaction in step (3) for precipitation to form lithium carbonate precipitate, which is recovered through filtration, washing, and drying to obtain a lithium compound.

[0120] In this comparative example, the leaching rate of nickel (Ni) is 80%, the leaching rate of cobalt (Co) is 80%, and the leaching rate of manganese (Mn) is 70%. The recovery rate of lithium recovered by the sodium carbonate precipitation method is 69.36%.

[0121] Compared with Example 3, due to the lack of electrochemical assistance, the leaching rate has decreased, especially the leaching rates of nickel and cobalt are not ideal. High-voltage electrochemical assistance significantly improves the leaching efficiency of metal ions, especially the leaching rates of nickel, cobalt, and manganese are significantly increased, almost achieving a complete leaching effect.

Claims

1. A method for electrochemically assisted green leaching of retired lithium-ion batteries, characterized in that: The specific steps include: (1) Pretreatment: disassemble the retired ternary lithium battery, take out the positive electrode material, clean and dry it, grind it to D50 = 2 μm ~ 5 μm, and place it in a reaction container; (2) preparing a leaching solution: placing a weak acid solution as a leaching solution in a reaction container to form a leaching system; (3) Electrode installation and electric field setting: Install inert electrodes in the reaction vessel, connect an external DC power supply, and gradually adjust the voltage according to the potential requirements of metal ion dissolution; (4) Nickel ion dissolution: adjusting the power supply potential to dissolve nickel ions from the leaching system to generate a leachate containing nickel ions; sampling and analyzing the ion concentration in the leachate regularly during the dissolution process, and when the ion concentration changes tend to be stable, the dissolution is completed; (5) Cobalt ion dissolution: After the nickel dissolution is completed, the potential is adjusted to dissolve the cobalt ions from the leaching system to generate a leaching solution containing cobalt ions; (6) Manganese ion dissolution: After the cobalt dissolution is completed, the potential is adjusted to dissolve the manganese ions from the leaching system to generate a leaching solution containing manganese ions. The potential is maintained to ensure that the manganese ions are completely dissolved to obtain a polymetallic noble solution; (7) Lithium extraction by precipitation: adding a precipitant to the solution obtained in step (6) to precipitate lithium carbonate, which is recovered by filtering, washing and drying to obtain a high-purity lithium compound.

2. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (2), the weak acid solution is a citric acid or malic acid solution with a concentration of 0.2 mol / L to 0.5 mol / L.

3. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (3), the material of the inert electrode is selected from platinum, titanium and graphite.

4. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (3), the initial voltage of the DC power supply is 0.5V to 3V.

5. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (4), during the nickel ion dissolution process, the power supply potential is 0.6V to 1.0V, and the nickel leaching rate is 90% to 98%.

6. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (5), during the dissolution of cobalt ions, the power supply potential is 1.2V to 1.6V, and the leaching rate of cobalt is 85% to 95%.

7. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (6), during the dissolution of manganese ions, the power supply potential is 1.8V to 2.2V, and the manganese leaching rate is 80% to 95%.

8. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: During the dissolution of the nickel ions, cobalt ions and manganese ions, the ion concentration in the leachate is sampled and analyzed regularly. When the ion concentration changes tend to be stable, the dissolution is completed.

9. The method for electrochemically assisted green leaching of retired lithium-ion batteries according to claim 1, characterized in that: In the step (7), the precipitant is a sodium carbonate solution with a concentration of 0.05 mol / L to 0.2 mol / L, and the recovery rate of the obtained lithium is 95% to 98%.

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